Continuous data protection
Health First, a group of hospitals and trauma centers, is using this strategy. The company runs 300 guest machines on 19 VMware ESX servers connected to a 150TB SAN. Health First uses IBM Tivoli for traditional backup, but because of its large virtual server infrastructure, the company decided to add a continuous backup system.
"We needed faster rebuild time in case of a disaster," says Jeff Allison, a Health First network engineer in charge of virtualization planning. "We use Vizioncore vRanger for hot backups of every virtual machine we have every night," he says. "Backups start at 5:00pm on two different machines and by 2:00am, we have backups for 230 boxes." The remaining 70 VMs are archived by the morning, and performance for the clinical applications is "not affected by the hot backups," Allison says.
Allison explains that the environment is more demanding in terms of uptime requirements for trauma centers and clinics, because data loss at a health facility could mean loss of life.
He describes one scenario where a controller failed on one test/development physical server that caused 80 VM development servers to be unavailable and unusable until a lengthy restore process could be initiated. On average, it could take several hours, he says. With a continuous backup system, the restore would now take about an hour and require perhaps one technician instead of several.
Indiana University presents another case for continuous backups, as opposed to VM mirroring or agents, because of the faster disaster recovery time and more granular data-archiving benefits.
A virtual machine is contained within a file that can be quiesced (archived incrementally) via a snapshot file, says Robert Reynolds, a senior software analyst at the university. "For the majority of our VMs, that quiesced file is stable enough to be then copied as a [disaster recovery] backup," he says. "Obviously, database servers and other transaction in-flight servers need more care in creating a DR backup.
"We run weekly jobs on each of our VMware ESX servers, using PHD's esXpress virtual backup appliances, to create the DR backups for our VMs," Reynolds says. "We create a copy on the local storage of the ESX server and we are in the process of developing a second phase to FTP the DR backup to another server where it will be picked up by Tivoli Storage Manager and sent offsite..."
A blend of approaches
"In the near term, a blend of these technologies might be the best approach -- taking an image-level backup and indexing those files continuously so that companies could do a single file restore, taking snapshots very rapidly, using a traditional backup application and VM agents to index the content on servers," says Gartner's Russell. "It does add more management complexity and another layer of abstraction to traditional backup, but the storage-resource tools are now catching up."